Broiler stunning methods examined by Dutch researchers

Researchers at the Wageningen University have completed a study to identify an electrical current and exposure duration to render broiler chickens unconscious instantaneously at slaughter using a head to cloaca water bath stunner.

Stunning legislationCurrent legislation demands that all birds are immediately rendered unconscious at stunning and that they remain insensible until death ensures. Use of the water bath is a legal electrical stunning method for poultry. In order for a stun to conform with the demands of legislature several aspects of the water bath method are of importance to its successful execution. The legal minimal current for an individual bird in the water bath is 100 mA.

The recommended minimum current for broilers in the EU increases quality defects (haemorrhages, broken bones) of carcasses and broiler meat. It is apparent that there can be a conflict between animal welfare and carcass quality using electrocution as stun-kill procedure. Therefore, the challenge still remains of providing an alternative stunning method with an effective threshold current that will induce consciousness and insensibility in broilers without compromising carcass quality.

StudyThe objective of the study was to identify an electrical current and exposure duration to render broiler chickens unconscious instantaneously at slaughter using a head to cloaca water bath stunner. The stunning methods were assessed using EEG and ECG. Meat quality after head-cloaca electrical stunning was compared with the currently applied water bath method in a commercial setting. Analysis of pH, colour, cooking loss and shear force from fillets during storage and scoring of blood splashes were chosen as parameters for product quality.

ResultsThe results showed that on the EEG recordings a general epileptiform insult was observed when applying a current of 100 mA combined with 100 Hz for a duration of 1.5 s. This general epileptiform insult shows a tonic, clonic and exhaustion phase, followed by a mix of spikes, alpha, beta, theta and delta waves. These birds may have been unconscious for approximately 20 s or more, according the cordimanes score analyses.

Within a confidence limit of 95%, taking into account the number of animals with a reliable EEG (n=27), the chance on an effective stun of all broilers lies between 0.9 and 1.0 with a current of 100 mA – 100 Hz – 1,5 s (AC block shape). The heart rate decreased significantly (p < 0.05) after stunning and recovered afterwards.

A general epileptiform insult showing the same signals was also observed on the EEG of birds stunned with 70 mA combined with 70 Hz for a duration of 1,5 s. According to the cordimanes score analyses, these birds may have been unconscious for approximately 15 s or more. Within a confidence limit of 95%, taking into account the number of animals with a reliable EEG (n=28), the chance on an effective stun of all broilers lies between 0.9 and 1.0 with a current of 70 mA – 100 Hz – 1,5 s (AC block shape). The heart rate decreased significantly (p < 0.05) after stunning and recovered afterwards.

The pH after chilling is significantly (p < 0.05) higher in the head-cloaca stunned group and the shear force lower (p < 0.01) compared to the conventional water bath stunned group, which means the meat is more tender. The percentage of fillets and legs without blood splashes is higher and the percentage with severe blood splashes lower to none.

ConclusionsIt can be concluded from this experiment that broilers are effectively stunned with the head-cloaca method by using a controlled current of 70 mA combined with 70 Hz or 100 mA combined with 100 Hz (AC block shape) for the duration of minimal 1 s. The meat in the fillet might be more tender and there are less blood splashes in both fillet and legs of bird stunned head-cloaca compared to birds stunned in a conventional water bath.